Margie Lynch is planning a new, high-performance home in Wyoming, a climate zone 7 location, where winter brings heavy snow and summer includes the risk of wildfires.
Given those realities, Lynch is trying to decide on two important details for the house: roof overhangs, and horizontal siding installed with a gap of as much as 3/8 in. between boards.
Lynch likes the look of no roof overhangs and she cites as an example a house designed by Ecocor called the Clover. Her plans for prefab exterior wall panels include insulated I-joists, a brand of exterior sheathing called Agepan DWD, a Mento 1000 water-resistive barrier (WRB), and horizontal clapboards charred in the fashion of shou sugi ban. The gap between siding boards would range between 5 and 10 millimeters.
“I’m looking for information on the performance/durability implications,” Lynch writes in this recent Q&A post.
If a zero-overhang roof is not a good idea, she continues, what’s a reasonable compromise to keep it to a minimum while ensuring the structure is durable? Does the gap between clapboards have implications for the building’s fire resistance? And how would the Mento WRB fare over time if there was a gap between siding boards?
Those are the questions for this Q&A Spotlight.
Two views on roof overhangs
Charlie Sullivan thinks that building a house with little or no roof overhangs will make it less durable, while installing gapped siding will make the house less fire-resistant.
He suggests improving durability by using fiberglass/gypsum sheathing instead of Agepan, and building a hidden gutter to minimize the amount of water that runs down the siding, then doubling up on the siding so the charred outerlayer is visible.
“Another option would be to hang out with building performance nerds long enough that your aesthetic sensibility…